Automatic telephone system



Feb. 28, 1928. 1,660,662

B. D. wlLLls AUTOMATIC TELEPHONE SYSTEM Original Filed March 16. 1921 4 Sheets-Sheet 1 Bernard DZ/u'z'ZZz's Feb. 28, 1928.-

B. D. WILLIS AUTOMATIC TELEPHONE SYSTEM Original Filed Marh 1a. 1921 4 Sheets-Sheet 2- TTLUFWLHFF Dunn-Hun Feb. 28, 1928. 1,660,662

B. D; WILLIS AUTOMATIC TELEPHONE SYSTEM Original Filed March 16. 1921 4. $heets-$heet 3 MME' Feb. 28, 1928. 1,660,662

a. o. WILLIS AUTOMATIC TELEPHONE SYSTEM Original Filed March 16, 1921 4 Sheets-Sheet 4 more efiicient and practical.

Patented Feb. 2c, 1928.

untrue BERN RD ,1). w pers, or at .reniifrrmnors, ASSEGNOR, BYE/EESNEASSIGNMENTS,

. TOAUTOMATIC ELEGTBIG and, or exercise, ILLINOIS, A oonroRA'rIoN 0F Janna-1' .WARE. 7

Application filedlvi-a-rch' 16, 192-1, Serial The present invention relates in generalto automatic telephone systems, but is con: iccrned more particularly with such systems as comprise a plurality o1": smallautoma'tic exchanges for usein rural communitles, such exchanges being commonly known as com munity automatic exchanges; and the ,ob]ect of theinvention generally speaking is to provide a variety of im rovements'ina system of this kind which end to make the same A special feature of the invent-ionrelates to improved circuit arrangements for an automatic connector switch whereby the operation of the connector under control eta calling line is prevented in case the 11116-15 grounded to such an extent as to interfere with the ringing and releasing operations which, in the ordinary course, will take place after the required connect1on is established.

A further feature is concerned with means in a connector switch tor'discriminati-ng between calls received over local lines, and calls received over incoming trunk lines. When a call is received over a local line the connector does not reverse battery in the calling line, but whenever a call is received over an incoming trunk line the direction of current flow in the trunk line is reversed.

lhereare a number or other features, not now specifically mentioned, which relate to various circuit refinements, and which together with the ones pointed out above will be fully described hereinafter, with reiterence to the acconuvanying drawings in which there is shown surficientof the apparatus'in a system embodying the invention to enable the same to, be described and understood.

Although the invention is applicable to systems differing in size and extent and employing any numberof different exchanges, it has been found convenient for purposesof illustration to show a system. comprising three small exchanges which are so located with respect to each other that the second exchange takes on the character of an intermediate exchange, and vcalls from the first exchange to the third exchange, and likewise from the third exchange to the first exchange are trunked through the second exchange. The first, or No. 1 exchange, is a manual ex change, while the No.2 and No. 3 exchanges are community automatic exchanges. According to the usual practice the abbrevia- AUTOM TIC rnrnrneun sYsTEM.

1%. 452,820. Renewed January 27, 1926.

group-of trunk lines sirnilar to the one' shown, each of which is providedwith trunk equipment such'as isillustrate-d at the right of Fig. l. -T-h'e calling device S "isc ommon to all of these't-runlrlines and may 'beconnected with-any one of them for the purpose of controlling'the automatic switches in the I d'istant'C. A. X. Y

'lxtthe No.12 exchange the trunkfline comprising conductors 245 and 25 terminatesin the incoming connector switch H, shown in Fig. 2, each of the other trunk lines in'the group being 'terminated in a similar switch.

These incoming connector switches 'have' access to the local lines in the'NoQQ exchange and also to trunk lines which extend to the No. 3 exchange, or the second CPA.-

i F 3 shows a local connector switch H, which. is one of a group of similar switches used by the subscribers in the No. 2 exchange In completing localconnections. The local connectors also have access to trunk lines extending to the "No. 3 exchange, and to'the group of trunk lines connecting with the No. 1 exchange, which includes the trunk line comprising conductors 24 and-25. i

In F ig. 4 there are shown two of the local lines which terminatein the No. 2 exchange, together with their associated individual line switches" C and C. The line serving the substations A to A", inclusive, is a party line, while the line of substation A is an in dividualline. Fig.4 also shows a" repeater. which is indicated by the reference character D and whichia associated with one of the trunk lines lconnecting with the N013 exchange. 'Ihisjtru'nk line comprises conductors 260 and 261- and extends through the re pea-.ter to normal conductors which are multi-pled in the banks oft'helocal and incoming connectors in the No.2 exchange. A branch extends from the repeater to the individual" connectors such as the connector H.

The line switch C is used on'calls incoming from the No. 3 exchange.

Fig. 5 is a detail showing-how theprivatebank contacts are connected in the trunking levels of the connector switches.

Most of the apparatusused herein is of a 'well'known type and consequently will not need .to be described ,indetail. The telephone'substations, including the manual substation A, Fig. 1, and theautomatic substations A to A, inclusive, Fig. 4, are of the usual type in common use. The automatic substations, however, are each. ro vided withcalling devices such asthe cal ing device S" and S for controlling the automatic switches. 1

The individual line switches C, .C and C are of the well known rotary type in which the wipers have no normal position and which move in a forward direction only.

As commonly constructed, these line switches have semi-circular banks containingtwentyfive sets of contacts, and two sets of wipers set at an angle of 180 degrees apart.

The localand incoming connectors, such as,

the connectors H and H are of the usual Strowger'vertical and rotary type, in which the bank contacts are arranged in horizontal rows, or levels and are operated'according to the, wellknown two wire system of control- The switch circuits are shown coni- I plete and as they contain a number of novel features they will be described in detail whichit has topert'orm.

hereinafter.- T-he repeater D is used for repeating impulses over the associated trunk line when-the same is :used, for calls to parties whose lines terminate in the No. 3

exchange, and is very similarto repeaters which have been commonly used beforethls; In view of the different switch-control and signalling circuits used in the present sys-v subscriber at substation A removes his receiver. a circuit is closed for line relay 2. The line relay 2 upon energizing, lights the lamp L in front of the operator. The operator, upon noting the lighted condition of lamp L, inserts the plug of an idle cord circuit, such as cord circuit 0, into the jack J.

When this is done the cut oil relay 3 energizesf andremoves the line relay 2 from the circuit. This'extinguishesthe lamp 1..

The lamp L is not lighted at this time because the relay 10 is energized over the subscribe'rsline loop and closes a shunt around the said'lamp. The operatorwill now throw her listening key in orderto converse with I the calling subscriber and, upon learning 7 that it isthe subscriber at substation A that the calling subscriber desires to be connected with,'she inserts the other plug of the cord circuit in use intoan idle jack associated with a trunk line to the nearer C. A; X., the

jack Jior example, and therefore the super-f visory lamp L becomes. lighted because there is no circuit closed at this time for relay 11. When the plug is inserted in jack J as just described a circuit is closed across trunk conductors 24 and 25 as follows: from trunk conductor 24 by way of the normally closed contacts controlled by spring 22 of key K, normally closed contact controlled by spring .20, spring 16 and its working contact, winding of the polarized relay 17, and

the normally closed contacts controlled by spring 21, to conductor 25 The effect. of closing this bridge across conductors 24 and 25 will now be considered; VVhen-the bridge is closed as "before described line relays 28and 29 of connector H at the main exchange energize in series by way of the following path: from ground through relay 29, normally closed contacts controlled by armature 41, resting contact of armature 39 and said armature, trunk conductor 25, and thence by way of previously traced bridge to conductor 24, armature 37 and its resting contact, normally closed contacts controlled by armature 40, normallyclosedcontacts controlled by-armature 52, and relay 28 to battery. Both relays 28 and 29, energize over thecabove circuit. The polarized relay 17, however, in the manual exchange, does not operate at this'time due to the fact that the current is flowing in the direction opposite to that in wh ch it must flow in orc er to operate the relay; [Relay 29upon energizing, operates release relay 30'- at armature 47 and its working contact.

Release relay 30, upon energizing, opens a.

llfi

point in the circuit of release magnet 49, and prepares the circuit of the vertical mag net 48.

lVit-h this condition eic isting, the operator throws her key K in such a direction as to operate'springs 20 and 21 thereby inserting the calling device S into the'bridgeacross the trunk conductors Y24 and 25 and removing the polarized relay 17 therefrom.. The operator may now operate her calling devicein accordance with the first digit 8 of the desired number and when she does so line relay 29 of the connector H is deenergized eight times momentarily. Before going farther a certain detail in connection with the opera'tion of relay 28 at this time will-be conthroughout the series or impulses. This,,

device opens the circuit. case the circuit for the verticalymagnet 48 is'closed as follows: irom ground by way of 1,eee,ea2

Isidered. It will be notedttlia-t when the bridge across conductors 24 and 25 is interruptedat the calling device S relay'28 as well as relay29-has its circuit broken. Now, ifitshould happen'that there is a very heavy ground upon the conductor- 24, relay 28 will not deenergize but will remain up however, known switches, does not ttlffeet the operation of the switch for the line relay 29 Operatesas usual. In the presentcase, however, the circuit of the vertical magnet is held 'open at armature 440i re- .lay 28 in case that relay does not deenergize. Thus it is seenth-at "if the ground on Conductor 24 isenough to prevent the deerergization of relay 28 it also prevents the mechanical operation of the connector.

Assuming I that the conductor 24 is not grounded sufficiently to prevent relay, 28 from operating when the circuit is first ins terrupted at the calling device S,;relays '28 and 29 both-deenergize as soonas the calling a-ninatures attracted throughout the vertical movement. Thecpera-tion of relay 3I serves to maintain the circuit of the vertical magnet intact at armature 53 and its work-- ing contac't fatter theofl' normal springs have shitted. as they do 'upon the first vertical step. Upon energizing, the relay 31 also places the resistance B into the circuit at armature 52 and removes relay 28 therefrom. V

This-operation increases the flow of current to relay 29 and also allows it cooperate over a circuitjthatis not so Inductive as it wouldwbe were the relay 28 :left in series. The entire removal cf the relay 28 from the circuit during impu-lsing prevents its operation during 'impulsing after it once falls back. 7 At the end of the vertical movement the slow acting relay .31 -.deen'ergizes and areinserts relay 28z-into the circuitand removes resistance vB therefrom while at armature 53 it shifts the operating circuit from the vertical magnet to the rotary magnet -69.

The operator nowope-rate her calling device in accordance with the gseconddigit 9 in the desired number and .w'hen-she does so the line relay 29 is deenergizednine times and thereby operates the rotary magnet -69 ever Ithe following, circuit-J, from That being the ground byway oat armature 4.7 and itsrest;

ing c ntactarmature Stand its working contact, vertical ofi' normal springs 56 and 55,"armatu're 53 and its resting contact, slow acting serles relay 32, normally closed con tacts controlled by armature -61,rest1ng con tact of armature -72 and'said armature, and

rotary magnet 69 to battery. By't heoperation of the rotary magnet the wipers are stopped around until they come to reston. the ninth set of contacts in the level cp- I In this case they come to rest on the contacts -83, in-

posi-te which they are raised.

elusive, ,these being the contacts in which the line of substat on terminates. The slow acting relay 32 is energized in series with the rotary magnet and retains its :armatures attracted throughout the rotary movement. At armature 59, relay 32, upon energizing, connects the resistanceli in mul-' tiple with relay 28 so as to provide a better impulsi-ng circuit for line relay 2.9, while at armature 60 it completes a circuit from grounded release tru-nk'co'nduetor 89 for relay 34. Relay 34, upon energizing,, P i.

pares the test circuit at .arm-at-ure65 ,and its working contact. At the end of the rotary movement the slow actingrelay deene-r- 1 gize's land, upon so doing, opens the circuit a of resistance R at ar-matnre 59', opens the original energizing circuit of relay 34 at ar mature '60, closes the-busytest circuit at the normally closedcontacts controlled by are mature 60, and at armatureGO and its rest- I! no ing contact prepares a circuit for the lower winding cf switching relay 35. J v V The operation now :dependsup'on whether the cal-led line is busy or idle Ii the'called line isbus-y there is :a ground potential upon the test contact v82 with which the test wiper -78 engagement. That being the case relay 34 does not deener'g'ize when-its circuit is shifted by the falling back of ar- ,matu're 60 of relay 32 but is maintained'energized overwthe following circuit: front ground by way ofbusy test contact 82, test w per 78,arma-t-u-ne 7 3 .and its resting coi h tact, armature 65' and its working contact,

normally closed contacts 'controlled by arrmature 62,, relay 33, normally closed contacts controlled by armature 616 of rotarymag'net =69, normally closed contacts (01 trolled by armature 60, and relay -34 to battery.-' Relay33 energizes over the above tracedlcirciuit and 1up'onso doing shifts its own circuit, and consequently that cf relay 34;. at armature-'62 'so that instead .of ground being supplied byway of test contact 82 it is supplied by way of release trunk conductor 89 land armature (1'2 and its working contact. This is done in order that the Icon nee-tor will not cut in on the busy line in case it :shoiuld zbeco'me 'idle' .later. A 'tur-i 7 ther resultjof the energization of :relay "33 is that it con-nects flat Ear-mature -63 a lead thedeenergization of relay 34. Relay 34 upon-deenergizing, completes at armature 65 the following circuit: from ground by way of release trunk conductor 89, armature 60 of'relay 32and its resting contact, lower winding of switching relay 35, resting contact ofarrhature 65 and said armature, resting contact of armature 73 and said armature, test wiper 78, test contact 82,*release trunk conductor 85,switching relay 203 of line switch C, Fig. 4, and stepping magnet 202 to battery. Switching relays and 203 energize in series over this circuit, and the latter clears the called line of its normal battery and ground connections in the line switch C. It may. be stated here that due to an interlocking device (not shown) be; tween the armatures of switching relay 203 v and line relay 201 thearmatures of switchbeing no longer supplied'with current due ing relay 203'are operated only about'halt way-at this time and consequently the wipers are not connected up. In the connector H, when the switching relay 35 energizes it establishes a locking circuit for itself at armature 72 in series with the rotary. magnet 69, at the same time disconnectin theiopcrating circuit from the ro tary magnet so'that in case the calling de vice is turned again the Wipers are not stepped around any further, prepares the circuit of the ringing relay 34 at armature 71, and at armaturesZO and 74 completes the connection to the line wipers 7 6 and 7 9.

The connection'is now extended to the desired called lineand in order to signal the called subscriber, the operator throws the key K to the opposite or ringing posltion,

in which position thespring 22 is operated.

remains energized and holds release relay 30 energized at armature 43, but relay 29,

to the ground placed upon conductor 24 by spring 22 of key K, falls back and operates the ringing relay 34.by way out-the following circuit: from ground byway of ar mature 47 of relay 29 and its resting contact, armature" 51 and its working contact,

armature 42'of relay 28 and its working contact, armature 71 and its working con tact, andringing relay 34 to battery. Ringin'g relay 34, upon energizing, operates ar bells are operated simultaneously, it is necessary that the ringin-g be done according to predetermined codes. This being the case, the operator repeats the operati-on 'as many times as are necessary to send out the code of substation A and ifthe subscriber the-reat does not answer immediately the code isrepeated as many times as maybe necessary to attract his attention.

lVhen the subscriber at'substation A responds he removes his receiver 'trom'the hook and as soon thereafter as the ringing relay 34 is in normal position a circuit is closed for the back bridge relay 27 by way of the.

normally closed contacts controlled by arma tures 37 and 39 of relay 26. ltelay 27, upon energizing, operates armatures 40 and 41; This operation places the upper talking condenser in the circuit and reverses the incon1- ing trunk conductors as'regards their con nection with relays 28 and 29. This results i in the operation of polarized relay 17 in the manual exchange, which, upon operating,

closes a circuit for supervisory relay 11 by way of impedance 18. "Supervisory relay 11, upon operating, extinguishes supervisory lamp L The operator, upon notingthat lamp'L is extinguished, knows that the called subscriber has answered. v

The calling and called subscribers, may now converse with each other in the usual manner and when the conversation is finished both subscribers replace their I'GCGlY'? ers. When the receiver is replaced at substation A the circuit of supervisory relay 10 is" broken with the resultthatthe super visory lamp L is lighted. The replacing of the receiver at substation A opens'the circuit of back bridge relay 27 of connector'H which, upon falling back, reverses the trunk conductors 24 and 25 back to normal. WVhen this is done polarized relay 17 retracts its armature and thus opens the circuit of'sup'er visory relay 11. j Supervisory relay 11, upon deenergizing, allows supervisory lamp L to becomelighted "again. The operator upon noting the lighted condition of lamps L and L pulls down the connection.

' lVhen the plug is removed from jack J the When the plug is removed of selector is opened'and the two relays accordingly d eenergize. When relays 28 and 29 deenergize they open at armatures 4:3 and 47 the circuit of release relay 30. Release relay 30, upon deenergizing, completes the following circuit for release magnet 49 :from

ground by way of armature 4 7 and its restmg contact, armature 51 and. 1ts resting contact, armature 38 and 1ts resting contact, ofl

normal spriiws 57 and 58 and release'ma net19 to battery. By the operation ofthe release magnet the switch shaft and wipers "stations'ilg and A and also resistance R of repeater D. If we assume, in the case just described, thatthe operator has operated the 0 key -K in such a direction as to operate spring 22 after the called subscriber has an swered and reversed the direction of cur rent flow in the conductors 2 1 and it is easily seen that spring 22'would have, in that a case, been connected by way of conductor 24 and the working contact'of armature and said armature, to relay 29. Accordingly this ground connection would not inthat case be effective tohold the relay 28 energized and it at that time the bridge across the conductors 24: and 25 were entirely opened relay28 would fall back with the result that the switch would be released. However, with the resistance It in the circuit, re lay 2,8 is held energiz'ed'and at armature 48 maintains release relay 8O energized. the other hand, the resistance It were omitted and the gap thus produced were bridged by a conductor of comparatively low resistvance the relay 29 of connector H would be slow to fall back, when the ringing key -is operated due to the fact that it is practically short crcuited by, the ground placed on spring .22. I sluggish action of line relay 29 at this time which of course would be very undesirable. T he other resistances mentioned in connection with resistance R are all placed where a they are for the same reason.

It will now be assumed that the subscriber .at substation Av desires. to obtain connec'- tion with the subscriber at substation A whose number is 90. When the subscriber at substation A removes l11S rece1ver a (311" cuit is closed for the line relay 201 of the.

This of course would result in a which thewipers of the line switch are standing is busy or idle. If the trunk line is busy there is a groundpotential upon-the test contactwithwhich the test wiper 209 is in engagement; theswitching relay 203 is short clrcuited and-the stepplng'magnet 202,

which interrupts its own circu1t,'1s oper ated in the manner of abuzzer to advance the switch wipers step by step in search of an idle trunk line. In the present case, hoW-,

ever, we may assume that when the call is v initiated the trunk line upon which thewipers of the'line switch are standing is idle. Under these clrcumstances when the pends upon whether the trunk'line upon line relay 201 .is-energized' the switching relay 203' is not short 'circuited and the stepping magnet 202 s: not operated. because of the hi h resistanceof said switching relayp The latter relay, however, is energized, grounds the test WlPGPQOQ at armature 206,

and at'armatures 207 and 208 disconnects the line conductors 84': and 86, from the wind-' ,ing otline-relay 201 and from ground re spectively, "and ext'end s ltheni by -way of wipers 210 and 211, bankcontacts 212 and 21 1, trunk conductors 101 and 103, armature'123 and its resting contact and the rest-f ing contact of armature l29 -andsaidarma ture, normally closed contacts controlled by.

armature 14 1 and'armature 125 and its resting contact to the windings ot line relays 115 andllS, respect1vely., L ne relays 113 and relay, 115 immediatelyenergize and the 1 Y 7 loo former operates release'relaymll from lease trunk conductor'102. at armature .133, thus establishing a holding circuit for the line switch C, the said ground extending back to release trunk conductor102 by way of armature 153 and its resting contact. :It

; is understood,of course, that this groundis placed upon release trunkconductor102-before. the slow acting line relay 201 has time to deenergizef By means of a groundpotential upon test contact 213 and its mane pics in the banks of the-line switches this holding circuit serves to render the connec-' tor-H busy to the other line switches and the busy potential also extends by way of private normal conductor 85 to multiple test contacts in the banks of "the connectors thereby guarding the line. against intrusion in the usual manner. The connector H is now ready for the usual impulses. 1'

his calling device 8' in accordance with the first digit?) of the desired number and when he does so the line relay '113 is deenergized nine times momentarily. At the first interruption .of-thecircuitproduced by the calling device S the line relay 115 also stalls The calling subscriber may now operate 1 and its workingcontact, 01f normal springs The operation of the line relays 113 and 115 of connector. H; is substantially like the operation of line relays 28 and 29 of connector H and consequently the detailed description given for the operation of relays 28 and :29 will enable an understand ng of the operation of-relays 113 and Each time'the line relay 113 is deenergized, assuming that relay 115 falls back on the first interruption of the circuit, the vertical magnet 149 is operated by way of the following circuit: from ground through armature 130 of relay llband its resting contact, armaturelS-ll 137 and 135, resting contact of arn'lature 141) and said armature, slow acting series relay the rotary magnet 150.

117, and vertical ii'i'agnet 149-to battery. By the operation of the vertical umgnet the switch shaft andwipers are raised step by step until the latter standopposite the ninth level of bank contacts. Theslow acting relay 117 is energized in series with the ver 'tical magnet and retains its armatures at:

tracted throughout the vertical movement. Atarmature 145 and its working contact, relay 117 retains the circuit ofthe vertical magnet intact after the vertical 011 normal springs have shifted as they do upon the first vertical step. A further result of the energization of relay 117 is that it operates armature 144 to include the resistance R in the impulsing circuit of the line relay 113. At the end of the vertical n'iovemei'it the slow acting relay 117 deenergizes andat armature 144 it replaces relay 115 in the circuit and removes resistance R? therefrom, while at armature 145 it shifts the oper ating circuit from the vertical magnet to The calling subscriber may now operate his calling device in accordance with the final digit 0 of the called number and when he doesxso the rotary magnet150 receives ten impulses over the following circuit: from ground by 'ay of armature 130 and its resting contact, armature 131 and its work ingcontact, of]? normal springs 137 and 186, arn'iature' 145 and its resting contact, slow acting series relay 118, resting contact of an mature 143 andsaid armature, resting conact of armature 159and said armature, resting contact of armature 155 and said arma-- cure, and rotary magnet 150 to battery. By the operationof the rotary magnet the'wipers 161464, inclusive, are stepped around step by step until they come to rest on the tenth set of contacts in the ninth level opposite which they are raised, being in this case the 7 contacts 165168, inclusive. S10 Y acting relay 1118 is energized in series with the rotary magnet and retains 'ltS armatures attracted throughout the rotarymovementand at ar mature 147 and its upper working contact completes a clrcuit for the slow acting relay 119. Relay 119upon energizingplacesrerecent-i2 sistance R in multiple with relay'115 so as to provide a better impulsing circuit, and at armature 151 prepares a circuit for the switching relay121. I Afurther result of the energization of relay 119 is that it includes resistance R in the circuit of the release trunk conductor 102, only, however, after the slow actingrelay 11811as, fallen back. At the end of the rotary movement the slow acting relay 118 deenergizes and at'armature 147 opens the circuit of slow acting relay 119 and removes a shunt from around resistance R5 The switching relay 203 of line switch C is connected in series with resistance R with the result that-the potential on release trunkconductor 102 and coin sequently on private normal (a)n(lu(':toif85 is varied, that is, instead 0 being at approxi- 1 mately the potential of ground as it was bc- -fore it is changed so as to stand at a'point between battery and ground. This operation enables a subscriber to call another subscriber Whose substation 1s located on the same-line as the substation of the calling sub- 1631s in engagement and the switching relay 121 being short circuited does not energize. Ainoment later, however, the slow'acting relay 11.9 deenergizes and at armature 1,51 Completes the following circuit from grounded test contact 167, by way of test wiper 163, armature 158 and its resting contact, armature 151 and its resting contact, armature 141 and its resting contact, and theuppcr winding of relay 116 to battery. Relay 116 energizes ovor the above traced circuit and just before armature 141 breaks away from its resting contact armature 143 makes contact with its working contact thereby closin I b the following locking circuit 7 from ground by way of armature 132 of release relay 114 audits working contact, lower winding of relay 116, resistance 3?, working contact of armature 143 and said armature, resting contact of armature 159 and said armature, resting'contact of armature 155 and said armature, and rotary magnet 150 to battery. Theoperation'of armature for 'relay 116:

148 in addition to'closing the locking (71t cuit' just described for relay 116 also disconnectsthe rotary magnet 150 from the operating circuitso that in case the calling subscriber should again turn his calling device he will not be able to cause the connector H to rotate the Wipers any further, 'A further result of the energization of relay 116 isthat' it connects at armature 142 a lead from the busy signalling machine B to the upper heavy talking conductor. This operation gives the calling subscriber an audible busy signal to inform him thatthe called line is, forthe time being, inaccessible; i

- In the present case,.however, wemay as, sume that the llne of substation A 18 1(l-l6 when called. :Thatbeing the case, when the 7 slow acting relay 118 deenergizes-at the end of the rotary movement, as has been previously described hereinbefore, a circuit is closed atithe normally closed contacts concontrolled'by armature 147 upper winding of switching relay 121,-working contact of armature 151 and said armature, resting contact of armature158an'd said armature, test wiper 163, test contact 167, private nor-v mal conductor 170, switchin'g'relay 215 of lineswitch C, and stepping magnet 216to battery. Switchingrelays121 and 215 energize in series over-the abovetraced circuit and the latter clears the called line of its normal battery and ground'connections in the' same manner as the switching relay 203 cleared the line of substation A in the previous call. In the-connector H the switching relay 121 upon operating opens the op-,

erating circuit and establishes a locking circuit for itself at armature 159. v This locking circuit extends by way of the working,

contact of armature 159 and said armature,

resting contact of armature 155 and said armature, to battery through rotary, mag net 150. As a further result of the energization of switching relay 121, it grounds the test wiper 163 at armature 158 inorder to protect the called line against intrusion, and

at armatures 156jand, 160 completes the connection to, the line wipers 161 and 164. instant later the slow acting relay119 (1e energizesand at armature 153 replaces di rect ground on release trunk conductor 102; and at armature152 removes resistance R from the impulsing circuit.

The connection has now been extended to the desired line and in order to'signah the subscriber at substation A operates his.

push button; lVhen' he doesso ground is placed directly on conductor 84 and resist-f will be sufiicient'tosay' that each tiinethe push button P'is operated that the line relay" 113 of connector H deenergizes and closes This operation is sub position.

the following circuit for ringing relay112:

from ground'by way of armature 130 and its resting contact, armature 181 and its working contact, oii normal springs 137 and 136, armature 145 and its resting contact, re-

la I 118 rin 'ino' rela' 112 workin contact 01 armature 1'38 and said armature, resting contact of arn'iature 155 and said armature, and rotary] magnet 150 to battery". 'The' ringing relay 112 isenergized over the above traced circuit but relay 118, however, on ac count of its comparatively small number of 'turns s not energized atthIStIm B. Rel-a 11-2 upon energizing, operates armatures'126 and 128 and thereby projects ringing cur rcnt out onto the called line. This of course rings the bellat substation Since there is only one subscriber on the line of substation A it willnot be necessary forthe calling subscriber to operate his pushbutton in accordance with any code. He will'nced only to repeat the operationat intervals until the called subscriber respondsby removing his receiver. Obviously when the push buttonP-is released the line relay 113 energizes again and opens *the' ringing circuit and generator is removed from the called'line; 4

Then the subscriber at substation A resp onds by removing his, receiver, a circuit is closed for back bridge relay 116 by way of armatures 126 and 128 and their resting contacts and the normally closed contacts controlled by armatures- 123 and 125. The calling and called subscribers may now converse with each other, the called subscribers transmitter beingisupplicd wit-h talking current' by way of the. upper and lower windings of back bridge relay 116.

Then the conversation is finished, the

two subscribers will replace their receivers.

When the rec'eiver is replaced at substation A the circuit of the line relays 1 13 and 115 is broken; Line relays 113 and 115 upon 'deenere'iz'ing, open the circuit of release relay 7 armature 124 and itsresting contact, resting contact Creator-m1 spring 134 and said spring, and release magnet148 to battery.

By theoperation 'oli-the release magnet the switch shaft and wipers are restored to normal position, the circuit otthe release magnet' being broken at ofl normal spring 134 by tlieshaft, when the latter reaches normal It; will now be assumed that the subscriber at substation A desiresjto obtain connection with the subscriber at substation 'sume inthe present case t-liat the connector i i switch H is the first one found to be idle and consequently theone selected. That being the case theline and release relays 113;, and 1141- of the connector H as well. as relay 115 energizes in the usual manner. We shall assume further that the connection to the l manual exchange inwhich. the line of sub-J statlon A terminates is obtained by calling 71. It will be remembered that there are a plurality of trunk lines. leading to the manual exchange. In'order to. be able to seize the first idle one of these trunk lines the connectors have incorporated in their circuits a rotary feature similar to that of the ordinary selector switch. In order to cause the connector switch to rotate, over to the next set of contacts, when one" is found 7 to be busy and not merely remain upon the contacts and send backa busy slgnal' thetWo private contacts are connected together as shown in Figure 5. In the last trunk line of the group, however, the two private contacts arecnot'jumpered together but are left open as in the case of an individualline. The result is that if a connector switch tries all of the trunks and finds them all busy, when it comes to the last one it tests it and upon finding it busy does not rotate any further but sends back a busy signal to the calling subscriber. Assuming that there are calling device in accordance with the digit ,inanner hereinbefore described. At the end of the rotary movement'the slow acting re- 1. This time the connector H! rotates its:

wipers one step at the-same time operating the slow acting relays 118 and 119. in the lay 118 deenergizes and completes at armature 146 the test circuit that is used only when the switch is operating as a selector to,

pick out an idle trunk line, and at the normally closed contacts controlled byarmature 147 completes the regular test circuit that determines whether or not the trunk upon which the wipers are standing is busy.

Theoperation now depends .uponjwhether the first trunk line is busy oridle; Assuming that it islbusy there isa ground potential present on the test contact 17 6, the switching relay 121 is short. circui'ted and since test contact 176 is multipled with test contact 175 the latter contact is' grounded also thereby opera the stepping rel y 2 ov he foll w ng circuitr t fqm gre nd. by Way of test'contact, 175 test wiper 162, ar1nature 157 and itsresting contact, resting contafi Qf armature lfiand-said armature, rest-1i ing contact of the armature'ot rotary magnet-150 and said armature, and stepping relay 120 tov battery.- Upon energizing, relay 120 establishes, a holding circuit for the A .slow relay 119at' ar1nature154, and at armature 155completes a circuit for rotary mags net 150. Rotary magnet 150, upon energize inig, steps thewipers 161464, inclusive, into engagement with the next set of contacts and r V operates its armature thereby opening the:

circuit of stepping relay 120. Stepping re:- i

lay 120 deenergizes and opens the circuitof rotary magnetl5 0 and also opens the-cir-.

cuit of slowacting relay 119. Rotary mag-- net 150 upon deenergizingflcloses again the circuit of stepping-relay 120. This cycle of operation is repeated over and over until an 1dle set of contacts 1s reached or until;

the last trunk of the group is reached in which case the two private contacts are not I i connected together. In the case, of the latter, the connector operates in the usual-manner to send ,back a busy signal to. the calling subscriber,.while it an idle trunk is reached it operatesinthe usual manner to extend the I connection to the called line,

" In the present case, however, we may assume that the trunk line terminating in bank contacts 1741-77,flinclusive, is idlewhen called. That being the case, when slow acting relay 1'18 deenergizes, it completes the following circuit for the switching relay 121:

from ground by way of armature 133 and its "working contact, normally closed-contacts controlled by. armature 1 17, upper winding of switching relay121, working contact of armature 151 and; said armature, resting contact of armature 158 and said armature, test wiper 163, test; contact176,

private normal conductor 89, armature of release relay 3O ofconnector H and its. restlng contact, lower wlndmg of swltching relay 26, ofli normal springs56 and 54, restme; contact of armature 4 1 and said armature, relay 31, and vertical magnet 48 to bat tery. The switchingrelays 121" and 26energize in series overthe above traced circuit and the latter clears the called line of its normal'battery and ground connections and extends it by way of arinatures 3-7 and 39 and trunk conductors 24 and 25 to the Operators Posi i n in he manual xc a e n th C nne tor H t e witchi relay 121 upon energizing, establishes the usual locks, lng c rcu t for itself and at armatures 1 56,

nd. .60 omple e the onne on. 9 he l ed linei V The su sc iber at substatien will now operate his push button in sa ne rnan ner s. W3S deSOI' b8d for the p sh: hut-ton P FBYAQQS e -rend. w en. 141Q$-S9- no n h' he connect r eperat s the usua subscriber at substation A is signalled conit has nothing in particular to do with the invention it need not be described in detail. It will be" sui'l'icient to say that the trunk conductors 88 and 90 ot the connector H arereversed according to the usual practice, when calls are extended from an automatic to a manual exchange by way or a two way trunk. That being the case, the relay 17 is operated as soon as the connection is extended to it over the conductors 2a and 25. This is done in order that the operator may get answering supervision as soon as she inserts the plug of the cord circuit into the'jack J and of course as soon asthe subscriber who has made the call hangs up thereby removing battery from the trunk conductors 2a and 25 the supervisorylamp of the cord circuit which is inserted into the'jacl: J lights to give the operator a disconnect signal'and she will pull down the connection in the usual manner. When the subscriber at substation A replaces his receiver the connector H releases in the usual manner which need not be here explained.

It will now be explained how a subscriber may call another subscriber whose telephone substation is located on the same line as that of the calling subscriber. For this purpose it will be assumed that the subscriber at substation A desires to obtain connection with the subscriber at substation A It will be assumed further that the code by which the sists or" three short rings.

WVhen the subscriber a't'substation A removes his receiver the line switch C opcrate in the usual manner topic'k outan idle trunk line leading to a connector, and we shall assume in the present case that the line switch upon operating obtains access to the connector H. That being the case when 555 the called subscriber operates his calling device in accordancewith the first digit 8 of the desired number the connector H raises its wipers 161464. inclusive, step by step until they stand opposite the eighth level of bank contacts. When the second digit 9 is called the wipers lfil-lfih nclusive, are rotated step by step until they come to rest on the ninth set of contacts inthe level opposite which they are raised. being in this case the bank contacts 17 1177 inclusive.

"While' the wipers are being rotated the slow acting relays 118 and 119 are energized in the usual manner. At the end, of the ro'- ta'ry movement the slow acting relay118 de-' energizes and at armature M7 removes the shunt around resistance R and completes at the normally closed contacts controlled by said armature the test circuit for the upper winding of relay 121. Obviously since the subscriber at substation A is calling another subscriber whose substation is on the same line the test wiper 163 comes into engageme'nt withthe private normal conductor 85' of the calling line switch. would result in the usual busy signal being Ordinarily this sent back but with a connector such as the connector H the including of the resistance" R in the circuit of release trunk conduct-or 1 102 results in the potential on the private normal conductor bein altered sulliciently.

to snow the switching ria 121 to energize. Switching relay 121 upon energizing, conipletes the connection through to' the called line which in this case is the same line as the one that is calling. It follows, theree gizes at once. I

The subscriber at substation A will now operate the push button P three times in accordance with the code of substation A2 and each time he does so ringing current is prof fore, that the back bridge relay 116 ener- 1 jected ou't'on the line and the subscriber at substation A is; signalled.

lVhen the subscriber at substa'tionri hears I his bell ringing he responds by removing.

his receiver. The two subscribers'may now converse with each other in an obvious in'anher. When the coi'iversatioii is finished both subscribers will: hang up their receivers and release. takes place in the usual manner.

It the subscriber at A were the calledsubs'criber instead of the subscriber at A the only difference iii the operation is that the push buttonis operated differently in order to produce a different code signal.

In the lower part of Fig. 4- there is shown the repeater D; This is a two'way repeater audit is used for connections to and from' another exchange that may be substantially I like the No.2 exchange which has just been described, The trunk line withwhich the repeater D is connected is the trunk line c'omprising conductors 260 and 261. will be remembered. that on tlie other end ofthe trunk line 260 and 261 there is another re v peate'r similar to repeater D and that access" iio to therepeater D and consequently tofthe" trunk line to which it is connectedis' obtained 2 by calling There may be, and usually are, a plurality of such trunklines'. Accordingly the two private conductorsassociated with each of thesetsot contactsinto which the trunk lines leading to repeaters such as repeater D terminate are tied together in order that the connectors may automatically rotate to pick out an idle trunk line. In the case of a connector calling the repeater D and also the other repeaters similar to it, the connector will switch the calling line through in the same manner as a selector, when an idle trunk'is foundi This is made possible by the springs 36 and 122 of connectors H and H, respectively. These springs are mounted on the respective switches in Such a manner that they are operated only when the switch wipers are stepped up to the tenth level of bank contacts.

Keeping the above facts in mind we shall assume now that the subscriber at substation A desires to obtain connection with a subscriber whose line terminates in the No.

' 3 exchange, reached by way of trunk line When the subscriber at substation A removes his receiver the operator is signalled in the usual manner and after she answers and obtains the desired information she inserts the other plug of the cord circuit in use into the jack of an idle trunk line extending to the nearer C. A. X., the jack J for example and throws the key K thereby inserting her calling device S into the circuit all in the manner previously extaking place.

plained. V

The operator will now operate her calling device in accordance with the first digit 0 of the desired, number and as a result the connector H raises the wipers 7 679, inclusive, step by step until they stand opposite the tenth level of bank contacts.

VVhen the calling device is again turned it will be in accordance with the second digit 1 of the desired number. In response to the calling of. the second digit the connector H steps the wipers into engagement with the first set of contacts in the level opposite which they were raised. After the end of the rotary movement, slow acting relay 32 deenergizes. Relay32, upon deenergizing, shifts the circuit of relay 34 so as to include relay 33. I

The, operation now depends upon whether the first trunk is busy vor idle. If the first trunk is busy there is a ground potential on test contacts with which the test wipers '77 and 78 are in engagement, it being remembered that in this case the two test contacts are connected together. That being the case, relay 34 does not deenergize when its circuit is shifted as explained but is maintained energized over a circuit that in .cludes relay 33, which is thestepping relay while the automatic rotary movement is Stepping relay 33 is energized now in series with relay 34 and at armature 62 shifts the circuit so that the two relays 33 and 34 are held up from ground on release trunk conductor 89 instead of from ground by way ofthe busy test contact. This operation is the same as that described in connection with the call in which the subscriber at substation A called a subscriber atsubstation A. A f urther result of the energization of stepping relay 33 is that it closes the following cirtest wiper 77 is in engagement, test wiper 77 V armature 61 and'its working contact, resting contact of armature 72 and said, armature, and rotary magnet 69 to battery, Rotary magnet 69 upon energizing, steps the wipers into engagement with the next setof contacts and at armature 66 closes a new circuit for relay 34, at the same time opening the circuit of the stepping relay. Stepping relay 33 upon deenergizing, opens the circuit of rotary magnet 69, which thereupon deenergizes and closes again the circuit of the stepping relay. If the second set of contacts is busy the same cycle of operation is repeated, and the operation continues in" this manner until, an idle'set of contacts is reached. I d V In the present case, 'however, we shall assume that the tenth or last trunk line or net 69 upon falling-back closes a. circuit for stepping relay 33 as usual in series with 1'elay'34 but because the test contact with which test wiper 78 is in engagement is not grounded, stepping relay 33 fails to energize and relay 34 deenergizes. Relay 34 upon deenergizing, completes the following circuit: from ground byway of the lower winding of switching relay. 35, resting contact of armature 65 and said armature, resting contact of armature 73 and said armature, test wiper 78, test contact 90, release trunk conductor 253, armature 239 (Fig. 4) and its resting contact, release trunk conductor 256, switching relay 217, and stepping magnet 218 tobattery. Switching relays 35 and 217 energize in series over this circuit but the energization of the latter has no function at this time. Switching relay '35 upon energizing, grounds the test wiper 78 at armature 73, and at armatures 70 and 74 completes the connection to the line wipers 76. and 79, and at armature 72 closes the usuallocking circuit for itself. When this locking circuit is closed the following circuit also is closed for switching relay 26: from ground by way of the working contact of armature 73 and said armature, test wipe 78, test contact 90, resistance R", test contact 89, test wiper 77, armature61 and its the trunk line terminating in contacts 8891, I

their working contacts, resting contacts of armatures 64 and 68 and said armatures, armatures 70 and 74 andtheir working contacts, line wipers 7 6 and 79, contacts 88 and 91, conductors 252 and 254, normally closed contacts controlled by armatures 250 and 251, to line relays 232 and 231 of the repeater D. The said relays immediately energize and close at armatures 247 and 248 multiple points in the circuit of release relay 230. Release rolay- 230, upon energizing, closes at armature 244 a circuit for relay 228. Relay 228, upon energizing, disconnects the release trunk conductor 253 from release trunk conductor 256 of the incoming line switch C and'connects it to ground. This ground potential extends by way of release trunk conductor 253, test contact 90, test wiper 7 8, and armature 7 3 and its working contact to switching relay of connector H to hold the said relay ener-.

gized. A branch of this circuit also extends by way of resistance R and test contact 89 to hold switching relay 26 energized. It is understood of course that this circuit is closed before the slow acting release relay 30 in the connector H has time to deenergize. Returning now to repeater D, when ground is placed on release trunk conductor 253 a circuit is closed for the lower or polarizing winding of electropolarized relay 235. This winding consistsof few turns of high resistance and is not able to operate the relay. As a further result of'the energization of relay 228 it not only shifts the connection of the release trunk conductor 253 as before explained, but also disconnects trunk conduct-'ors 260' and 261, at armatures 23,8 and 240,'fromtheconductors 255 and 257, respectively, and connects them to a closed bridge in the repeater D extending as followsz from armature 240 and its working contact, by way of impedance 227,1upper winding of electropolarized relay 235, working contact of armature 246 and said armature, to the working contact of armature 238 and said armature. It will be remembered that on the other end of the trunk line 260 and 261 there is a repeater similar to repeater D and associated therewith is a line switch similar to line switch C That being the case, when the bridge is'closed across trunk line 260 and 261 at repeater D the line switch on the other end of the trunk, similar to line switch C is operated in the usual manner to pick out an idle trunk line leading to a local connector. ized relay 235 is not operated at this time because the current flowing in its upper winding opposes that flowing in its lower winding. 7

The operator may now operate her calling device in accordance with the remaining digits of the desired number and when she does so the connector 1n the distantexchangeto ground.

The electropolarsteps its wipers into engagement with the desired set ofcontacts, the impulses being repeated at armature 246 and its working contact. Upon the sending of the first impulse, line relay 232 also falls back and at arn'ia-ture 248 closes a circuit for slow acting relay 229 by way'of armature 245 andits working 'contact. Upon energizing, relay 229 shuntsv relay 232' with resistance R at armature 241, opens I at armature 243 a point in the circuit used for relaying ringing impulses so as to prevent possible interference, and. at armature 242 closes the bridge across trunk conductors 260 and 261 by a more direct path so as to improve the impulses sent to the distant connector. At theend of the series of impulses slow acting relay 229' falls The operator in ay now operate her ringing key in the :11 manner and-when she does so relay line of repeater D deenergizes and line'relay 232 remains energized. With this condition existing trunk con'ductor260 is connected to ground by way of the following circuit: from armature 23? and its working contact, by way of armature246 and its resting contact, working contact of armature 249 and said armature, and the resting contact of armature 243 and said armature 7 This of course has the same effect on conductor 260 and consequently the relay in the connector switch on the other end of said conductor as though a ringing key were actually pressed zit-repeater D to ground the conductor 260. -Conductor 261 at this time is grounded over the bridge previously traced through repeater D except that the resistance 1* is now included in this bridge since: the armature 246 is at this time in a deener 'ized position. The utility of resistance R is the same as was described for the resistance R at the operators position. It will now be seen that the repeater- D relays the circuit conditions into the connector switch on the other end oftrunk line 260 and 261 tocause the connector to send out a ringing current. The operator will repeat the ringing operation as many times as may be necessary in order to attract the attention of the called subscriber. Whenthe called subscriber answers he causes 'battery to be reversed in the trunk conductors 260' and 261 in a manner that will be explained fully hereinafter. When the current flow is reversed. in trunk conductors 260 and 261 it is also reversed in the upper winding of the electropolarized relay 235 includedin a bridge thereof. The two windings of relay 235 which heretofore have opposed each i if j reverses the conductors 252 and 254 at armatures 250 and 251 as regards their connection with line relays 231 and 232. The final result is that polarized relay 17, Fi 1, is operated to give the operator answering supervision in the usual manner. The two subscribers may now converse with each other in the usual manner. When the conversation is finished both subscribers replace their receivers, the replacing of the receiver at-substation A bringing in the usual disconnect signal. lVhen the receiver is replaced at the called substation in thedistant exchange the current flow in conductors 260 and 261 is reversed back to normal with the result that relay 239 retracts its armature thereby reversing the current flow in conductors 252 and 254oto normal. This relights the lamp L in the usual manner and the operator pulls down the connection.

Attention may now be called to the fact that the local connectors in the two C. A. X.s are not arranged to reverse battery when a call is answered. Due to the numerous other duties, including the completing of reverting calls that the connector must per form it has not yet been found desirable to I arrange a connector of this type to reverse battery. In order to take care of the reversing of battery on interexchange calls a novel arrangement is made use of. Since the equipment in the two ends of the trunk line 260.261 is identical a'description of the operation of one will serve for the other. Accordingly it willnow be assumed that a call is coming from the No. 3 exchange by way of trunk line 260261. When the line switch C extendsthe connection to a connector the connector H for exam le the I switching relay 217,.in addition to closing the usual circuits, closes also at armature 280 a circuit to wiper 281. Now when the called subscriber answers, the back bridge relay 116' energizes and at armature 172 closes the following circuit: from ground by way of armature 175 of switchingrelay 1 21 and its working contact, working contact of armature 172 and said armature, conductor 104, contact 262, wiper 281, working contact of armature 280 and said armature, conductor 258, and reversing relay 226 to battery. Reversing relay 226 energizes and at armatures 236 and 237 reverses the trunk conductors 260 and 261 as regards their connection with the line relays'at connector B. This obviously results in the reversal of the direction of current flow in the said conductors.

We shall now assume that the subscriber at substation A desires to obtain connection with some subscriber located in the exchange on the other end of trunk conductors 260 and 261. lVhen the subscriberfat substation A removes his receiver to initiate the call line switch C is operated to pickout an idle connector switch. We shall assume in the subscribers loop, and release relay 114 is energized and grounds the release trunk conductor 102,thereby establishing the usual holding circuit, and the connector is made ready for operation in the usual manner.

The subscriber may now operate his calling device in accordance with the first digit 0 in the desired number and when he does so the connector H steps its wipers up step by step until they stand opposite the tenth level of bank contacts. 2

The calling subscriber may now operate his calling device in accordance with the second digit 1 of the desired number and thereupon the wipers are rotated one step.

The operation now depends upon whether the first trunk is busy or idle. Assuming that the trunk is busy the slow acting relay 118, upon deenergizing, closes at armature 146 the following circuit for stepping relay 120: from ground by way of the connecting jumper to the test contact with which test wiper 162 is in engagement, test wiper 162,

armature 15? and its resting contact, resting contact of armature 146 and said armature, resting contact of the armature of the rotary magnet 150 and said armature, and stepping at the same time operates its armature to break the circuit of stepping relay 120. Stepping relay upon deenergizing opens the circuit of the slow acting relay .119 and also opens the circuit of the rotary-magnet .150 which, thereupon, deenergizes and closes again the circuit of the stepping relay 120.

The operation now depends upon whether the second set of contacts is busy or idle. If it is busy the same cycle of operation is repeated over and over until an idle or un- I grounded set of contacts is reached. We shall assume in the present case that the trunk line terminating in contacts 181-184, isthe first one found idle and consequently the one selected. That being the case the arrival of test wiper 163 upon test contact 183, closes the following circuit for switching relay 121: from ground by way of the upper winding of switching relay 121, working contact of armature 151 and said armature, resting contact of armature 158 and From this point the call continues in the said armature, test wiper 163, test contact 183, release trunk conductor 253, armature 239 oi relay 228 of the repeater D and its resting contact, release trunk conductor 256, switching relay 21'? or line switch C and steppin magnet 218 to battery. Switching relays 121 and 217 energize in series over the above traced circuit. Switching relay 217 upon energizing, clears the called line of its normal battery and ground connections. In connector H switching relay 121 upon energizing, completes a locking circuit for itself at armature 159 in the usual manner and at armature 158 grounds the release trunk conductor 253 in order to make it busy immediately. This ground also extends by way of resistance R, test contact 182,v test wiper 162, armature 157 and its working contact, tenth level spring 122 and its working contact, switching relay 111, working contact of armature 159 and said armature, resting contact of armature 155 and said armature, and rotary magnet 150 to battery. Upon energizing, switching relay 111 extends the calling line by way of armature 123 and their working contacts, resting contacts of armature 126 and 128 and said armatures, armatures 156 and 160 and their working contacts, line wipers 161 and 164, contacts 181 and 184, conductors 252 and 25 1,v normally closed contacts controlled by armaitures 250 and 251 to line relays 232 and 231 calling subscribers loop and prepare the.

switch for operation in the usual manner.

same manner as previously described in which the subscriber at substation A called a subscriber whose line terminates 1n the distant exchange and, consequently, it need not be described in detail.

In the two calls described, that were for a subscriber whose line terminates in the No. 3 exchange, no mention is made about what happens when all ten trunk lines such as the trunk line 260261 are busy. Such explanation will now be given.

In the case of the connector H when its wipers arrive on the tenth set of contacts in the tenth level or the contacts 88-91, inclusive, and find them busy relay 33 energizes again and closes the usual circuit for the rotary magnet 69 but owing to the high resistance of R the rotary 'magnet cannot energize and consequently'the usual busy signal is sent backto the calling operator; V

When the wipers of connector H arrive on the tenth set of contacts in the tenth level and find them busy the usual circuit is closed for the stepping relay 120 but owing to the high resistance oi R the said relay' cannot energize. A moment later slow acting relay 119 falls back and closes the usual busy test circuit with the final result that an audible busy signal is sent back to the calling subscriber .to inform him that he cannot, for the time being, 0b-

tain the desired connection.

Having fully described and ascertained the features of my invention what is considered to be new and desiredto have pro tected by Letters Patent will be pointed out in the appended claims. a

lVhat I claim as my invention is:

1 In atelephone system, a calling line, an automatic switch controlled over the said calling line to connect with a called line, the switch being normally operable regardless of anabnor-mal condition of the line, and

nect with another line regardless of said abnormal condition, and means effective to prevent the operation of said switch in case' the abnormal condition is such as to prevent the subsequent release of the switch.

3. In a telephone system, telephone lines, some in normal and some in abnormal condition, an automatioswitch having different operating and releasing characteristics, the switch being operable over any calling line whether such line is in normal condition or not, while the switchcan be released only it the calling line is in normal condition, and means for'preventing' the operation of said switch over a calling line whose condition is so abnormal that if the switch were permitted to operate its subsequent release would be interfered with.

4. In a telephone system, telephone lines some in normal and some in abnormal condition. an automatic switch-having different operating and releasing characteristics, the switch being operable over any calling line whether such line is in normal condition or' not, while the switch can be released only if the calling lineis in normal condition, means in said switch for testing the condition of a calling line in case it is attempted to operate said switch over such 11116:,31101 means for preventing the operation-of the said switch in case the test indicatesthat i tthe switch were permitted to operate its subsequent release would be interfered with.- 7

5.- In a telephone system, telephone lines,.

I some in normal and some in abnormal condisaid switch being adapted to perform its main functions whether the calling line 1s in normal condition or not, while it can per form certain of its auxiliary functions only if the calling line is in normal condition, and means for preventing said switch from per forming its main functions under control of a calling line'whose condition is so abnormal that the subsequent performance of the auxiliary functions of said switch would be interfered witln 6. In a telephone system, a telephone line having a ground on one conductor thereof, an automatic switch adapted to be controlled over said line to connect with another line, and means effective to prevent the operation of said switch in case the said ground is of such low resistance that it would prevent the subsequent release of said switch, al

though so far as the said ground is concerned the said switch could be operated.

7. In a telephone system, an automatic switch, a calling line and means for extending it to said switch, a relay in said switch connected from one conductor of said line to the non-grounded pole of the exchange battery, a second relay in said switch connected A from the other conductor of said line to ground, means for-interrupting the line circuit at the Subscribers station to cause de energizations of said second relay, neans for operating said switchcontrolled by said second relay, a non-inductive resistance, and a relay energized during the operation of said switch to substitute said resistance for the said first relay.

8. In a telephone system, an automatic switch, a calling line and means for extending it to said switch, a relay in said switch connected from one conductor of said line to the non-grounded pole of the exchange battery, a second relay in said switch connected from the other conductor of said line to ground, means for interrupting the line circuit at thesubscribers station to cause deenergizations of said second relay, means controlled by said second relay in response to said interruptions for operating said switch to connect with a called line, a device at the subscribers station for opening a normally closed connection between the line conductors and for connecting one conductor to ground, the said second relayv being deenergized while the first relay is held up, and

means controlled by said relays jointly'for' device at the subscribers station for opening a normally closed connection between the line conductors and for connecting one conductor to ground, the said second relay being deenergized while the first relay is held up, means controlled by said relays jointly for signalling the called subscriber, a relay energized when the called subscriber answers to reverse the two conductors of the calling line with respect to their connections to said first and second relays, means for releasing said switch efiective when both said relays are deenergized, and a resistance connected ,in shuntof said normally closed connection nect it instead to the wipers of said switch,

and another circuit for energizing said switching relay effective in case said trunk line is taken for use by one of said other switches. 1

11. In a telephone system, a calling line a group of trunk lines, an automatic sideswitchless connector switch controllable over the calling line to select said group of trunk lines among other lines accessible to said switch, a motor magnet and means for operating the same automatically to causesaid switch to select the firstidlc trunk i group, said means including astepping relay for sending impulses to said i'nagnet, means for holding said relay energlzedin case all of said trunks are busy, and contacts con: trolled by said relay for connecting the calling line with a source of busy" signalling current. v

12. In a telephonesystem, two kindsof lines, an automatic switch adapted for use by a calling line of either kind for extending connection to a called line, and means controlled by the response of the called subscriber for reversing the direction of current fiow in the calling line only in case such calling line is of a particular kind.

13. In a telephone system, a cor.inector switch, local lines and incoming trunklines having access to said switch, there being means for-operating said switch over either a local line or a trunk line to connect with a called l1ne, andnieans in said switch for reversing the direction of current flow in the tillQCtlOIi of the calling subscriber ll'lCElSG the call comes over a trunk line, while if a said local line is calling the current flow therein is not reversed.

14. In a telephonesystem, a local line and an incoming trunk line each terminating in an individual switch, a local trunk line accessible to both switches and extendingvto a connector switch, an extra conductor in said local trunk line accessible only to the'indi vidual switch which is associated with said incoming trunk line, means for operating either individual switch to connectwith said local trunk line and for operating said connector to connect with a called line, and relay mechanism operated when the called subscriber answers in case he has been called by way of said incoming trunk line for reversingthe direction of current flow in such trunk line, said mechanism being controlled over said extra conductor.

15. In a telephone system, a" two-way trunk line terminating in an automatic switch and accessible ,at the same 'end :to

- other switches, a line relayiii the first switcli controllable over said trunk line to cause the operations of said first switch, a cutvofi relay and a circuit for energizing it after the switch has operated to disconnect said line relay from said trunlgand' another circuit including a second winding on said cut-off relay "for energizing it to I cut-offsaid line relay when said trunk line is seized by one 0t saidother switches.

16. In a telephone system, a, connector switch having a test relay adapted to pull up and connect up the line wipers responsive to a non-busy potential on the test contact of a called line, a second test relay adapted to pullup and place a busy tone on the calling line responsiveto a busy potential on the g test contact of acalled line. circuit arrangements such that said first test-relay is connected to the selectedtest cont-act after said switch has been operated. and circuit ar-- rangeinents such that said second relay is then connected to the selected test contact in case said first test relay does not'opcrate.

17. In a-telephone system, a connector switch having wipers, a test relay, means for moving said wipers into engagement with the contacts of a desired line a slow-acting relay held energized during thesaid move ment of said wipers, another relay, means for operating said other relay at the end .of the movement of said wipers to open'the circuit of said slow-acting relay and to con- Iiect up said test relay in ELClICHlt including that-est contact of the called line, means controlled by said test relay and. inresponse to its finding an idle potential on the test contact of a line for completing the connection to said line, and means controlled by said slow-acting relay when it falls back for opening the test circuit extending through said test relay. e

18. In a telephone system, a connector holding switch having wipers, two test relays, means for operating. said switch to bring said wipersinto engagement with thecontaets of a desired line, aslow-acting relay energized during the time 111' which said wipers are being brought into engagement with the-de- I sired vcontacts, means operative upon the cessation of the operation or" said switch for contact, and means controlled by said'slowv acting relay when it falls back for'opening the said circuit for the saidfirst test relay and for connecting up the second of said test relays .in a circuit extending from the other pole of the exchange battery to said test contact. a

' 19.1In a telephone system, a two-way trunk, an automatic impulse relaying .re-

peater associated with said trunk "at one end thereof, means including automatic switch es for setting up connections over said trunk ineitlier direction, and means in sa d; re-

peaters responsive to the answering of the called. subscriber for reversing the curreiit' flow in either endof said trunk when that end is thecalling end. i 20. In atelephone system, an automatic switch, a-gcallingfline. means including;

another automatic switch for extending a connection from, said llIlG'tO the first of said switches, .areleasetrunk conductor 'forw said first switch-,ineans-tor holding said other switch in its operated position resp'on-l I s ve to a holding potential on. said'c'onductor;

a relay in said first switch connected between onepole of the exchange battery and one line conductor, another relay in said first switch connected from the "other pole of the exchange battery to the other line con-y] ductor,-;-a circuit for energizing said relays in series over the calling line when said, connection is extended to said first switch,

a release relay, contacts controlled thereby for placing a holding potential 'onsaidre-' lease trunk conductor, contacts controlled by one of said'line relays for closing'an energizing circuit for saidreleasei'elayi and-con tacts on the other'line relay "for placing "a ducto direct. a v

21. Ina telephone. systenn an automatic sw tch, subscribers linesdivided into' groups accessible thereto, means for operating said fotential on said release trunk conswitch vert-ically in order to selectone of said group'saiid for then rotating said sw tch into connection with-one of said lines;

a test; wiper torsaid switch, a test relay in i said switch, a slo'w acting relay energized during the rotary movement-of said switch, a third-relay for connecting said testwi'per;

-to said test relay, and a circuit "f O'r'JSaid third relay closed by said slow-actingrelay;

22. In a telephone system, anautomatic switch, called lines accessible thereto divided into groups and subgroups, said switch having a'directively' controlled movement to select groupsand subgroups and an automatic movement to select an idle line in the selected subgroup, a relay energized only during the movement of said switch in selecting subk groups, a testwiper'io'r said switch, a test relay for said switch, a third relay for connecting said testwiper' to said test relay, a. 7 Circuit for energizing said third relay coin "lay energized during the movement of said switch in selecting a group of lines, a slowactingrelay energized in response to the energization of the first relay, a testwiper, a

testrelay, means fortdeenergizing said first? relay at the end of said directively controlled movement, means'controlled -by said first relay when it ,deener'gizes for connecting said test relaytovsaid test wiper, for lIlltlatnlg the, automatic hunting movement of v the switch, and for openingv the circuit of said slow-acting relay, ineansfor maintaining.

said slow-acting relay energizedduring the automatic hunting movement of the switch, and means controlled by said slow-acting relay when it falls back for disconnecting saidtest relay from said test wiper. o

1 24; In a telephone system, an automatic switch, called lines accessible thereto divided into groups, said switch'having a directively controlled movement to'select a group of lines and an automatic hunting-movement to select an idle line in the selected group, arelay energized during the movement of said switch inselecting a group of lines, a slowacting relay energized 1n responseto the en- 'ergization of the first relay, a test wiper, two

test relays, means for deenergizing said first relay at the end of'said directively' 'controlled movement, means controlled by said first relay when it deenergizes for connecting the.

' ing said slow-acting relay energized during a the automatic hunting movementv of the switch, and means controlled by said slowa'cting relay when it falls back fordiscoin necting the first test relay .fronrthe test wiper and for connecting the second test re-V l lay thereto.

first of said test relaysto said test wiper, for

initiating the automatic hunting movement,

of the switch, and for opening the circuit of said slowacting relay, means for maintain- In a; telephone ,system,-.a trunk line connecting van automatic exchange with a manual exchange, means including automatic switches in the automatic exchange for completing connections over said trunk line originatingat either exchange, a polarized relay at the manual exchange individual to said trunk line, a supervisory signal controlled by said relay, and means operated automatically in both automatic to manual and manual to automatic" calls forreversing the direction of current flow in said trunk line to actuatesaid relay when the. automatic subscriber involved hangs 'up his receiver.

26. In a telephone system, a trunk line connecting an automatic. exchange with a manual exchange, means including automatic switches hithe -automatic exchange.

for completing connections over said trunk line originating either exchange, a polarized relay at the manual exchange individual to said trunkline, asupervisory si nal controlled by said relay, and means op'- erated automatically in an automatic" to manual call to actuate said relay when the automatic subscriber involved replaces his receiver and in a manual to automatic call to deactuate or actuate said relay when the automatic subscriber involved removes or replaces his receiver, respectively;

27. In a telephonesystem, a trunk line ex-- tending between an automatic and a manual exchange, an'automatic switch at said automatic exchange, an operators position at said manual exchange, means including said switch for establishing a' talking connection between said exchanges from the automatic exchange over said trunk line, means including. said switch for establishing a tally mg connection between said exchanges fromf the, manual exchange over. said trunk line,

a. polarized relay at 'said'manual' exchange individual to said trunk line,- and means in said switch in calls from the automaticex change to the manual exchange for actuate ing said relay when the automatic subscriber involved replaces his receiver and in calls from the manual exchange to the automatic exchange for. actuating said relay when the operator seizes said trunk line, fordeactuating' said relay when the automatic suba scriber involved removes his receiver aiid for,reactuating said irelay 'when theauto' matic subscriber ceiver. m

28.--In a telephone system, acalling line,

involved replaces his rean automatic switch under the control of said calling line and having two line relays, oneof said line relays being'coiinectecl be tween one conductor of the calling-li-neand.

ground,and"the other line relay being con nected between the other conductor ofthe calling line and the u-ngrounded pole of'the exchange battery, an operating circuit for said switch including normally closed con f tacts on both said relays, and means respon 

